13B.4 Comparison of airborne SFMR, Dvorak satellite and best track maximum surface wind estimates

Thursday, 1 May 2008: 8:45 AM
Palms E (Wyndham Orlando Resort)
Peter G. Black, SAIC/NRL, Monterey, CA; and S. Mullins, C. S. Velden, M. D. Powell, E. W. Uhlhorn, T. Olander, and A. Burton

The objective of this study is to compare GPS dropsonde-calibrated, remotely-sensed SFMR maximum surface wind against the objective, satellite-based Advanced Dvorak Technique (ADT) and forecaster-derived, consensus Best Track (BT) maximum surface wind (Vmax) estimates. The study is based on a 10-year data set from 1998 to 2006 that includes 178 radial flight legs from 53 separate flight patterns in 17 tropical cyclones using a consistently calibrated SFMR instrument combined with the most recent geophysical model function derived after the 2005 hurricane season.

Initial results show that mean of the Probability Density Function (PDF) for BT Vmax estimates from tropical storm to CAT4 hurricanes exceeds that from the SFMR Vmax distribution by 6 m/s, representing a 12-15%, or one storm category, overestimate. BT and SFMR Vmax estimates show close agreement for CAT5 storms. The issue of under sampling of SFMR Vmax due to flight tracks missing the true Vmax is addressed using two years of processed airborne Doppler radar data. Anew pressure-wind relationship derived using SFMR data shows a similar offset compared to BT pressure-wind relations used by forecasters.

Initial results show that the ADT derived Vmax tends to be an overestimate for weak CAT1 and CAT2 storms while underestimating CAT 4 storms. There is a bimodal distribution of ADT Vmax estimates with more CAT 1 and CAT 3/4 storms than indicated by SFMR Vmax and fewer ADT CAT2 storms than indicated by SFMR Vmax. This suggests that ADT may have trouble accurately identifying the eye feature as it is first appearing and transitioning storms from CAT 1 to CAT 3 intensity too quickly. Preliminary comparisons with conventional Dvorak technique Vmax estimates suggest that this effect is less pronounced. The present study suggests the possibility of reducing the uncertainty in tropical cyclone maximum surface wind estimates to the level of scatter in the SFMR vs GPS dropsonde comparisons by tuning future Best Track and satellite based ADT surface maximum wind estimates to those produced by SFMR surface wind measurements.

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